Azadirachtin effect

Punzo, F. The effects of azadirachtin on larval stages of the oak toad, Bufo quercicus (Holbrook), Florida Scientist, 60(3) 158-165, 1997. 

Azadirachtin has several effects on a number of economically important species of insect pests, including feeding deterrency. 

Neem extracts, pure constituents (i.e. azadirachtin) and formulated products showed positive results against Tetranichus mites [279-283]. Less polar extracts were considerably more toxic than polar ones or cold-pressed neem oil or commercial neem oil, and reduced the fecundity of the mites on treated plants and the survival of nymphs hatched from treated eggs application of pentane extract or neem oil in sublethal concentrations, caused growth disrupting effects on the nymphal stages and ovicidal effects. Quantification of the insecticidal substance azadirachtin in the extracts revealed that this compound was not the most active principle against the mites [284]. 

T. confusum. The iodolactones were found to be weaker antifeedants, unlike the iodolactones of precocenes, which were the only semisynthetic compounds having a strong antifeedant effect. An excellent antifeedant against T. confusum is compound 81, which had an activity that is comparable to that of azadirachtin (213). Its enantiomer 82 was only slightly less active.54... 

Investigation of the contents of the acetone extract of T. tomentosum yielded in total six clerodanes. Although there were some slight differences, all six clerodanes 127—132 were active antifeedants against both S. litura and Plutella xylostella with feeding inhibition values between 60 and 85% at lOpgcm-2 and 55-75% at 5 pgcm-2. Teuflin (128) was the most effective. However, compared with azadirachtin, the effectiveness is still about 10 times less.74... 

Numerous other insect antifeedants have been isolated from a variety of sources. One way to search for these is to look for a plant that would appear to be good food for nearby insects, but that is not eaten. Two compounds that are about as effective as azadirachtin are shown in 11.23.138 Mycotoxins can be as effective as azadirachtin in some cases, as in the following example (11.24).139 It would be instructive to try this technique on some of the highly invasive exotic weeds found in the eastern United States. It is possible that weeds such as kudzu, Lonicera japonica, Alliaria petiolata, and Celastrus orbiculatus, contain antifeedants that might be used on crops in the area where they are pests. Their harvest for this purpose... 

The three metabolites assayed produced the same effect on the insect used that the control (a commercial extract of the neem tree, containing 2% of azadirachtin), although at higher concentrations. 20a-hydroxy-tingenone was the most active compound among the three assayed. Pristimerin shows also a high antifeedant activity together with molt effect suppression. 

Polonsky et al [112] reported the effect of forty-six natural and semi-synthetic quassinoids, on feeding of tobacco budworm (HeliotMs virescens). Their activity is compared to that of the well-known antifeedant azadirachtin from Azadirachta indica Juss. 

No adverse effects on fetal development were observed in rats fed the compound azadirachtin (0.5 mg/kg) for two generations, or in rats fed large doses (1.5 g/kg) of azadirachtin daily on days 6 to 15 of pregnancy. 

In pregnant rats orally administered 0.5,1, or 1.5 g/kg of the compound azadirachtin daily on gestational days 6 to 15, no significant adverse effects were observed on fetal development, number of implantations, post-implantation loss, or other reproductive parameters. Some minor malformations were observed in high doses but were not compound- or dose-related (Srivastava and Raizada 2001). 

No adverse effects on reproductive function or fetal or pup development were observed over two generations of rats fed diets containing the equivalent of 5, 25, or 50 mg/ kg of the compound azadirachtin daily (Srivastava and Raizada 2007). 

Srivastava, M.K., and R.B. Raizada. 2007. Lack of toxic effect of technical azadirachtin during postnatal development of rats. Food Chem. Toxicol. 45(3) 465-471. 

Use N. can be used in plant protection as a natural antifeedant and insecticide. These uses are due to azadirachtin. The oil is superior in action to the pure active principle this is due to the stabilizing effect of the oil and to its content of other active substances. Aqueous seed extracts or emulsions of the oil have traditional uses in India as insecticides and represent an important alternative to the use of synthetic neurotoxins (for mechanism of action, see azadirachtin(s)). In India the yearly production of the oil amounts to ca. 80000 t/a N. however, the larger part is used for the production of soaps. 

Plant sesquiterpenes and other terpenoids aie major detenninants of insect-plant interactions (2i 16V Many insecticidal and antifeedant terpenoids are epoxides including monoteipene Q2, 18. sesquiteipene QQ, 19-23). diteipene (Jl, 24) and triteipene derivatives (25-27) typified by the potent antifeedant azadirachtin (28-30). Most biolo cal effects have been determined with Lepidoptera and non-chrysomelid Coleoptera. Occasionally, the same compound, while normally inhibitory to herbivores, may for adapted insect species or at low concentrations have a stimulatory effect (13). Insects, in turn, synthesize their own defensive (21, and pheromonal (22) terpenoids. Plants may utilize insect pheromones such as the sesquiterpene alarm pheromone, rranj-B-famesene, in their own defense (34. 35). Inhibitory cyclic sesquiterpenes (Table I) and diterpenes (Table II) for insect herbivores have been identified from at least 28 genera of the terpenoid-rich Compositae. These studies were largely confined to extrafloral tissues. 

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